1. Field of the Invention
This invention is directed toward novel compounds of 1,1-diphenyl-2nitroalkanes, i.e., nitropropanes and nitrobutanes, substituted at their respective para-positions by C.sub.4 -C.sub.6 alkyl and ethoxy, having utility as insecticides which are highly effective in combatting various difficult to control insect species such as lepidoptera, e.g., southern armyworm.
2. Description of the Prior Art
Since the discovery of the insecticidal properties of DDT, scientists have attempted to identify materials which are as effective as DDT and related chlorinated hydrocarbons but which are also biodegradable in living systems to excretable metabolites.
Attempts at accomplishing this goal by substituting alkyl and alkoxy substituents for chlorine in the basic diphenyl structure of DDT and related chlorinated hydrocarbons have been reported in the literature.
Thus the goal of identifying biodegradable insecticides structurally similar to DDT has been achieved, but none of the compounds reported exhibit the same broad range of insecticidal effectiveness as DDT. Specifically, none of the reported biodegradable DDT - like insecticides, e.g., diphenylalkanes containing an alkoxy or alkyl substituent, is effective at low application rates (100 ppm or less) on, for example, the important agronomic class of insects, lepidoptera.
For example, methoxychlor which represents the DDT basic structure with methoxy groups in the p,p' positions instead of chlorine as reported by I. P. Kapoor, et al., J. Ag. Food Chem., 18, 1145 (1970) is biodegradable in living systems but has essentially no activity against the important lepidopterous insect, southern armyworm (See Table I below) even at the high rate of 500 ppm. R. L. Metcalf et al., Bull. Wld. Hlth. Org., 44, 363 (1971), disclosed new biodegradable DDT analogues possessing p-alkyl, p'-alkoxy substituents in place of chlorine. The more insecticidally effective of these compounds reportedly was methyl methoxychlor and methyl ethoxychlor. Nevertheless, in our test (See Table I below) these compounds, at the high application rate of 500 ppm, did not control southern armyworm. T. A. Jacob et al., in J. Org. Chem. 16, 1572 (1951) reported that no activity was observed against the southern armyworm when p,p' - alkoxy substituted diphenyl-nitroalkanes were used as insecticides.
Additionally, U.S. Pat. No. 2,716,627 discloses 1-aryl derivatives of 2-nitro-1-p-isopropylphenylalkanes as being adapted to combat insects including the southern armyworm. However test data reported in said patent on representative compounds, e.g., 2-nitro-1-p-isopropylphenyl-1-p-ethylphenylbutane, 2-nitro-1,1-bis-(p-isopropylphenyl)butane and 2-nitro-1-p-isopropylphenyl-1-tolylbutane revealed that in fact insecticidal compositions containing same were totally ineffective having zero percent kill at application rates of 100 ppm against southern armyworm larvae. Testing these compounds under the same test conditions as the compounds according to this invention revealed essentially the same results, i.e., compositions containing compounds embodied in U.S. Pat. No. 2,716,627 showed little or no effect on southern armyworm larvae.
Additionally, Metcalf et al. Bull Wld. Hlth. Org., 38, 633-647, (1968) in evaluating the relationship of chemical structure to the mode of action of DDT and DDT-like compounds and to the mechanisms of insect resistance to DDT and DDT-like compounds positively state that insect activity of such compounds is optimal when the phenyl groups thereof are substituted by small relatively non-polar groups such as CH.sub.3, CH.sub.3 O, C.sub.2 H.sub.5 and C.sub.2 H.sub.5 O. Metcalf et al., further positively state that when these compounds have phenyl substituents with larger alkyl groups in the p and p' positions, that is larger than C.sub.2 H.sub.5, they were found to be completely insecticidally inactive.
Thus the prior art indicates that DDT-type compounds possessing alkoxy and alkyl substituents would be biodegradable but would most likely be unable to control, for example, the lepidopterous class of insects at economic levels of application, particularly where alkyl substituents are larger than C.sub.2 H.sub.5. Therefore, quite unexpectedly and in sharp contradistinction to these hypotheses, the novel compounds of this invention while possessing the biodegradable p-alkoxy and p-alkyl substituents and a large (C.sub.4) alkyl group are nevertheless most effective in controlling a broad spectrum of insects, e.g., the lepidoptera insect species, highly destructive of important field crops. Effective control of this class of insects, e.g., the southern armyworm has been obtained at the low economic application rate of 100 ppm.